Electric cut-out



July 17, 1928. 1,677,720

G. F. LINCKS ELECTRIC GUT-OUT llunnL 22 George F Lrl'cKs DE /M Z7 His Attorr-leg.

Ait.:

j. "1 is a part longitudinal section lPatented July 17, 1928.

UNITED STATES PATENT ori-"ica GEORGE FEED LINoKs, or PITTSEIELD,

ELECTRIC COMPANY, A CORPORATION 0F NEW YORK.

ELEe'rEIc cU'TfoUT.

Application filed December 17, 1924. Serial No.

The present invention relates to electric safety devices, and more especially to thermal cut-outs or fuses of high capacity.

ln the act of blowingvof an electric fuse, a solid conductor explodes or'is converted into gas in a very liniitedtime interval and the severity of such explosions and the incident noise and projection of fiame is in proportion to the amount of energy flowing at the instant in the circuit protected by On account of the serious objecuses, they have the fuse. tions to the behavior of been heretofore restricted in'their use to the circuits of relatively low capacities, thereby necessitating the use of the very much more expensive circuit breakers for the protection of the /liighercapacity circuits.

The object of my 'invention is the provision of an electric fuse arrangement which shall function satisfactorily to prot-ect high capacity circuits and which shall perform its intended function without causing injury to persons or vicinity. l j

One ,embodiment of the invention is shown in/th'el accompanying drawing in which Fig. and part side Fig. 2 is a things in its elevation of a fusible cut-out;

top plan view thereof with certain parts in section; Fig. 3 is a part longitudinal section and' part side elevation of the fuse cartridge and one of its receiving contacts; Fig. 4 is a right-hand elevation of the cut-out as indicatcd in Figs. l and 2," Fig. 5 is a crosssection taken on line 5-5`of F ig. l; Fig. 6 is an end view of fuse cartridge; andF ig. 7 isan enlarged cross-section of the fuse link.

The cut-out shown in the drawing is designed to protect an 'electric circuit carrying normally two hundred amperes current at fifteen thousand volts `and to function properly and without injury under fa momentary rush of current of upwards of seventy-five thousand kilowatts. l

It comprises a closed'tank A of heavy chamber, but

possibility o'fr or cartridgev 4 end cap 2 has a keyholefslot horn fibre, with the outer end portions threaded for the reception of heavy end caps 2 and At about one-third of its length from the right-hand end, as shown in Fig. 3, the barrel interior is divided yby a partition 4 into an explosion chamber 5 and a spring chamber 6. To secure the partition 4 against displacement, the barrel is counterbored at its right-hand end to provide an internal annular shoulder 7, against Whichdthe partition is pressed by an insulating sleeve 8 which bears at its outer end against theend cap 3. A plurality of large holes 9 through the barrel' and sleeve 8 about the spring chamber 6 are provided for the yfree iow of through duringthe time period of blowing of the fusible element 11. The partition 7 has al centralaperture 12 normally closed by a plunger 13. s he plunger 13 has` a circular head 14 larger than the aperture 12 Iso that when held against the partition 7 it effects a practical clos'ure of `the former. A semicylindrical projection 15 from the head extends through the aperture 12, and a similarly shaped clamping plate 16 is secured thereto by set screws 17 forl the purpose of velectrically and mechanically engaging the end ofthe fusible element 11 therewith. The plunge'rhead 14 has a peripheral groove 18 in whichy one end of a contractile helical while the other end of the latter is secured in a similar manner to a circular projection20 on the inside of a thimble 20 screwed upon the end 'cap 3. The plungerV 13 landl the ,end thimble 20 are also Iconnected by flexible shunts 21 to rotect the spring 19 from `the heatingielpects of ,current therein.

The fusible element 11 .is soft metalA or alloy withone end straight to be Vreceived by the clamping connection 15, 16, while the other end is a flat head 22. It i's also provided with the. usual reducedcrossl section latv23 neartthe clamping connection 15, 16. The left-hand 24 inits endm 25 whereby the fiat head 22 of the or drawn spring 19 is secured,

wall fusible element 1,1 may be passed oil into and out of'that provided with :100 a fiat strip of l by aplurality of hinged throughthe' fiange and engage The fusible link 'a steel wire 27,

case the soft metal of the link used has linsuflicient tensile strength normally to resist the tension yexerted by .The tank A is a the spring 19. lrectangular box constructed to withstand severe shocks incident to the explosive action fof the fuse, with a lid 28 adapted to be firmly held in place bolts 29 mounte on the sides of the box. v Insulator bushings 30 for the circuit wire connectors 31 exten through the opposite end walls `of the tank and are secured in place by flanged meta rings 32 :cemented to the outside of the bushings and bolts or screwsl 33 which pass the-end walls of the tank. To make the joint oil-tight, a packing ring 34 is interposed, as indicated in Fig. 3. v f

The circuit wire connectors 31 comprise metal shells 35 ada ted to be independently soldered to the endg of the circuit wires or cables, knurled clamping rings 36 swivelly engaging the shells 35 and screw-threaded upon nuts 37 which are screwed upon the outer ends `of conductor bars 38 carried by the bushings30 and connected at their inner ends to fulcrum blocks 39 for the stationary contacts D. The fulcrum blocks 39 are provided at their outer ends with washers or clamping plates 40 adapted to receive between them the` ends of flexible shunt conductors 41 and are held in clamping relation by set screws 42. Packing rings 43 are interposed between the`outer washers 40 and the shoulders 43 on the bushings 30 at the bottoms of their end recesses 44. The inner ends of the fulcrum blocks 39 are provided with recesses 45 and cross-bars 46. The stationary contacts D comprise rectangular sheet metal plates 47 with the upper edge 48 curved outwardly and stud brackets 49 riveted. centrally to the outer surfaces. The studs of brackets 49 are suiciently small to enter the recesses 45 of the fulcrum blocks 39 with ample clearance to permit limited universal tilting of the former. The studs are cleft longitudinally to straddle the crossbars 46 and are themselves provided with cross-bars 50 which serve 1n conjunction with cross-bars 46 to prevent the longitudinal displacement of the contacts while permitting a certain amount of free axial move- -ment thereof. In order to yieldingly press the contacts D toward each other, helical springs 51 are interposed between the outer surfaces of the plates 47 and the washers d 3. The cranks l other by 'on the tank A to thereby retain 40 and about the fulcrum blocks 39. By attachment of the flexible shuntl conductors 41 to the plates 47, the springs 51 are re-d lieved from carrying cident heating effects.

Thel elevating means C for.. moving the cartridge fuse B through the oil in the tank and into and out of engagement with the `stationary contacts D consists of a rock shaft 52 journaled in the end walls of the tank and provided with three cranks 53, 54 and 55, the first two of which are positioned in the planes of the end caps 2 and 3 of the current and dits linfuse and carry 'at their free ends U-shaped` leaf springs 56 with apertures in the legs thereof adapted to engage with rounded d studs 57 located at diametrical points on the outer plane surfaces of the end caps 2 and material and held in fixed relation to each a bolt 58 passing therethrough parallel to the shaft 52. 'Both the bolt I,and

53 and 54 are of insulating y shaft are encased in nsulation 59 toprvent v l their becoming conductors for arcing currents. The crank at the outside end of the shaft 52 carries at its free end the operating handlev 60 which is transversely movable therein under control of a helical spring 61 which tends to move it toward the end of the tank and its tip 62 into locking relation with shoulders or projections 63 and 64 the fuse B in or out of engagement with its contacts D. When the lid 28 of the tank is off, the fuse may be swung up above the top thereof (see Figs. 4 and 5) to permit it to be removed and replaced by another without the operator coming in contact with the bath of oil in the tank.

The tank AA 65, and at its ends about the circuit wire connectors 31 are sheet metal canisters 66 with flanged tubular sections 67 extending through the outer end walls which are adapted to be soldered to the lead sheath .of the circuit wires or cables. Packing rings 68 are interposed between the flanges of the tubular sections 66 land the end walls of lthe canisters 'and set screws 69 inserted. The top walls of the canisters are pierced to permit insulating material to into after which stopper y serted. A vent pipe 71 is connected to. one end of the tank to permit the latter to relieve itself of gas pressure without scattering of oil.

Electric protective devices must function tov protect a circuit from excess ow of current, whether that excess be small as in the case of a gradually applied overload or very great as 1n the case of a short circuit and any and all conditions between those extremes. The function of the tension spring 19 accordingly is to pull the fuse link 11 in two in case of a gradual softening or weaken- 's lined with sheet insulation be poured there-v plugs are inlll() lll ing thereof in case of the gradually applied overload. When a short-circuit occurs on the circuit protected, the spring 19 performs no funct-ion since the generation of gas pressures in the explosion chamber 5 is so nearly instantaneous that the plunger `13 is displaced in the direction of the spring more rapidly than the spring can act. Upon the disruption of the link 11 under short-circuit flow, a very vigorous arc springs between the severed ends thereof or the terminals to which it was connected. However, as it approaches the aperture 12 in'the partition 7,`

it is cooled and extinguished by the violent rush of oil that takes place through the aperture 12 as the plunger 13 moves backwardly. The explosive action that takes place upon a fuse blowing on short-circuit is so violent and the momentary gas pressures so great that the hardy fibrebarrel 1 of the fuse cartridge would4 almost certainly be shattered were it not for the cushioning action of the bath of plate tank. My cut-out has been found in practiceV to be entirely successful in instantaneously interrupting 'the 1flow of electrical energy equivalent to a hundred thousand horse power without injury to itself or other objects and without flame or dangerously hot gases escaping therefrom.

`While I have shown and described the best embodiment of the invention known to me, I do not desire to lbe lrestricted thereto. What I claim as new and desire to secure by Letters Patent of the United States, is 1. An electric cut-out comprising an insulating shell having a transverse partition provided with a contracted opening and dividing the interior sion proof chamber and a spring chamber, arc suppressingfluid ing said explosion proof chamber, met-al contacts secured to the ends of said shell, a fusible element extending through said-explosion proof chamber from one of said contacts, a. displaceable terminal connected to the opposite end of said fusible element and disposed adjacent said contracted opening, and spring means disposed in said spring chamber and exerting tension on said displaceable terminal.

2. An electric cut-out comprising an in-` sulating shell, a contact terminal mounted` on one end of shell and having. a spring connected to the inner side thereof, a second contact terminal fixedly hmounted on the other end of said shell and provided with a keyhole slot, and 'a fusible element connected at one end to said spring and provided at the other end with a head adapted to pass through and be retained against the tension of said spring by the walls of the contracted portion of said keyhole slot.

3. An electric cut-out comprising an insulating shell, fuse vterminal contacts mountoil and the stout boiler thereof into an explo-- within and surround' of said shell, line terminal contacts for electrically engaging said fuse terminal contacts, and means for supporting said line terminal contacts universally tiltable and yieldingly movable toward and from each other.

4. An electric cut-out comprising a cartridge -fuse having terminal" contacts mounted on the ends thereof, stationary line terminal contacts adapted to engage the ends of said fuse terminal contacts, a fluid container in which said line terminal contacts are mounted, and a rock shaft operable outside said container fixed thereon adapted to engage opposite 4ends of said cartridge fuse for depressing and elevating said cartridge fuse through the fluid into and out of engagement with said stationary contacts.

5. An electric cut-out comprising a shell of insulation enclosing a fuse chamber therein and provided with an expulsion yaperture through a wall thereof, a fuse terminal disposed in said chamber remote from said expulsion aperture, a second fuse terminal disposed adjacent said aperture and displaceable outwardly therefrom, a fusible element connecting said ,terminals through said chamber, and arc suppressing fluid normally filling said chamber and adapted to be ex,

ed upon the ends `pellcd by the gases of fusion through said expulsion aperture against said displaceable fuse terminal and into intimate contact with any ensuing electric arc. l l

6. An electric cut-out comprising a -shell of insulation enclosing a fuse chamber and provided in opposite side walls with a plurality of minute holes and in an insulating end Wall with an expulsion aperture, a fuse terminal xed t0 one end of said shell 'opposite said expulsion aperture, a second fuse terminal normally closing said expulsion aperture and displaceable outwardly therefrom, a fusible element connecting said fuse rterminals and extending through said chamber. an arc suppressing fluid surrounding, said casing and normally filling said chamber and adapted to be expelled therefrom by the gases of fusion through said expulsion aperture against said displaceable terminal and into intimate contact with any ensuing electric arc.

7. An electric cut-out com rising a tank of arc supressing fluid, a cylincii'ical shell of insulation adapted to be immersed in said fluid and having a plurality of minute holes in its walls through which said fluid may enter and completely fillthe chamber thereof, a transverse insulating Wall fixed therein at one end of said chamber and provided with a contracted expulsion aperture, a fuse terminal fixed to said casing opposite said transverse Wall, a second fuse terminal normally closing said expulsion aperture and displaceable outwardlytherefrom, a fusible and having spaced arms im l clement extending through said chamber from terminal to terminal and serving'nor mally to retain said second terminal in closing position and springs mounted vin said shell and connected .to said second fuse terminal to effect its displacement upon Weakening of the fusible element underoverload.V

8. An electric cut-out comprising a cylindrical shell of insulation, metallic caps secured to opposite ends thereof, a transverse Wall of insulation fixed Within said shell to divide the interior thereof into a fuse cham'- ber and a spring chamber and provided with an expulsion. aperture, afuse terminal normally closing said aperture and displaceable into said spring chamber, a fusible element yout of said spring Amy hand this llthday of Dec.,

connected to one of said caps, extending through said .fuse chamber and connected to said displaceable fuse terminal to hold it in closing relation to said aperture, springs connected to the otherof said caps and to said displaceable fuse terminal,a bath of arc suppressing iuid in which said shell is adapted to be immersed and said shell having provisions to permit restricted flow of said fluid into and to fill said fuse chamber and to permit unrestricted flow of said liquid into and chamber,

,v In- Witness whereof. I have hereunto set G. FRED LINCKS. 

